Earlier today, we noticed that the number of people online on was falling, which wasn’t typical or expected, so we began to investigate.

isn’t a network like a conventional phone or IM network – instead, it relies on millions of individual connections between computers and phones to keep things up and running. Some of these computers are what we call ‘supernodes’ – they act a bit like phone directories for . If you want to talk to someone, and your app can’t find them immediately (for example, because they’re connecting from a different location or from a different device) your computer or phone will first try to find a supernode to figure out how to reach them.

Under normal circumstances, there are a large number of supernodes available. Unfortunately, today, many of them were taken offline by a problem affecting some versions of . As relies on being able to maintain contact with supernodes, it may appear offline for some of you.

What are we doing to help? Our engineers are creating new ‘mega-supernodes’ as fast as they can, which should gradually return things to normal. This may take a few hours, and we sincerely apologise for the disruption to your conversations. Some features, like group video calling, may take longer to return to normal.

Stay tuned to @ on Twitter for the latest updates on the situation – and many thanks for your continued patience in the meantime.